Computers have become an integral part of society. Every day people become more dependent on computers to facilitate both work and leisure activities. A significant drawback to computing technology is its “digital” nature as compared to the “analog” world in which it functions. Computers operate in a digital domain that requires discrete states to be identified in order for information to be processed. In simple terms, information generally must be input into a computing system with a series of “on” and “off” states (e.g., binary code). However, humans live in a distinctly analog world where occurrences are never completely black or white, but always seem to be in between shades of gray. Thus, a central distinction between digital and analog is that digital requires discrete states that are disjunct over time (e.g., distinct levels) while analog is continuous over time. As humans naturally operate in an analog fashion, computing technology has evolved to alleviate difficulties associated with interfacing humans to computers (e.g., digital computing interfaces) caused by the aforementioned temporal distinctions.
A set of structured keys is one of the earliest human-machine interface devices, traditionally utilized in a typewriter. This interface system was adapted to interact, not with mechanical keys and paper, but to trigger discrete states that would be transmitted to a computing system. Thus, a computer “keyboard” was developed, allowing humans to utilize an existing, familiar interface with unfamiliar technology. This eased the transition into the computer age. Unfortunately, not everyone who wanted to utilize a computer knew how to type. This limited the number of computer users who could adequately utilize the computing technology. One solution was to introduce a graphical user interface that allowed a user to select pictures from a computing monitor to make the computer do a task. Thus, control of the computing system was typically achieved with a pointing and selecting device known as a “mouse.” This permitted a greater number of people to utilize computing technology without having to learn to use a keyboard. Although these types of devices made employing computing technology easier, it still did not address the age old methods of communicating—handwriting and drawing.
Technology first focused on attempting to input existing typewritten or typeset information into computers. Scanners or optical imagers were used, at first, to “digitize” pictures (e.g., input images into a computing system). Once images could be digitized into a computing system, it followed that printed or typeset material should be able to be digitized also. However, an image of a scanned page cannot be manipulated as text or symbols after it is brought into a computing system because it is not “recognized” by the system, i.e., the system does not understand the page. The characters and words are “pictures” and not actually editable text or symbols. To overcome this limitation for text, optical character recognition (OCR) technology was developed to utilize scanning technology to digitize text as an editable page. This technology worked reasonably well if a particular text font was utilized that allowed the OCR software to translate a scanned image into editable text. At first, this technology had an accuracy of about 50 to 60%, but today it has progressed to an accuracy of near 98 to 99% or higher. OCR technology has even evolved to the point where it can take into account not only recognizing a text character, but also retaining paragraph and page formatting and even font characteristics.
Subsequently, OCR technology reached an accuracy level where it seemed practical to attempt to utilize it to recognize handwriting. After all, why transpose handwriting to text via a keyboard if it can be directly digitized into a computing system? The problem with this approach is that existing OCR technology was tuned to recognize limited or finite choices of possible types of fonts in a linear sequence (i.e., a line of text). Thus, it could “recognize” a character by comparing it to a database of pre-existing fonts. If a font was incoherent, the OCR technology would return strange or “non-existing” characters, indicating that it did not recognize the text. Handwriting proved to be an even more extreme case of this problem. When a person writes, their own particular style shows through in their penmanship. Signatures are used, due to this uniqueness, in legal documents because they distinguish a person from everyone else. Thus, by its very nature, handwriting has infinite forms even for the same character. Obviously, storing every conceivable form of handwriting for a particular character would prove impossible. Other means needed to be achieved to make handwriting recognition a reality.
One of the earlier attempts at handwriting recognition involved “handwriting” that was actually not handwriting at all. A system of “strokes” or lines was utilized as input into a computing system via a “tablet” or writing surface that could be digitized and translated into the system. Although attempts were made to make the strokes very symbolic of a printed text letter, the computing system was not actually recognizing handwriting. In fact, this method actually forces humans to adapt to a machine or system being used. Further developments were made to actually recognize true handwriting. Again, if a system was required to match every conceivable variation of a letter to one in a given database, it would take enormous processing resources and time. Therefore, some of the first advances were made in areas that had at least a finite, even though rather large, group of possibilities such as mail zip codes.
Technology has continued to develop to reach a point where a system can accurately and quickly interact with a user. This has led to an increased focus on systems that can adapt readily to a multitude of users. One way of achieving this type of system is to utilize a “classification” system. That is, instead of attempting to confine data to “right” or “wrong,” allow it to fall within a particular “class” of a classification. An example of this would be a user whose handwriting varies slightly from day-to-day. Thus, a traditional system might not understand what was written. This is because the system is attempting to make a black and white assessment of the input data. However, with a classification based system, a negative response might only be given if the handwriting was so varied as to be illegible. A disadvantage of this type of system is that the classifiers must be manually trained in order to increase the accuracy of the classifier.
Despite the vast improvements of systems to recognize natural human inputs, they still require that a user follow some type of linear space and/or time sequencing in order to facilitate recognizing a user's input. In other words, a user must follow a line such as a line of text or must draw an equation in a particular time sequence. If a user decides to annotate or correct a drawing or an equation at a later point in time, these traditional types of systems can no longer accurately recognize the input. Because of these limitations, traditional systems also cannot handle situations where inputs are scaled and/or re-oriented. The systems tend to be complex as well and require great effort to improve their performance.